High-density contact holes

ABSTRACT

Methods for patterning high-density contact holes and contacts are described herein. Embodiments of the present invention provide a method comprising depositing a first dummy layer over a substrate to form a first pattern; depositing a second dummy layer over the substrate to form a second pattern, the second pattern overlapping the first pattern at a plurality of locations; etching the first and second dummy layers to form a plurality of posts at the plurality of locations; forming a dielectric layer over the substrate; and etching the posts to form a plurality of contact holes in the dielectric layer. Other embodiments may be described and claimed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication Nos. 60/888,134, filed Feb. 5, 2007, and 60/908,022, filedMar. 26, 2007, the entire disclosures of which are hereby incorporatedby reference in their entirety.

TECHNICAL FIELD

Embodiments of the present invention relate to the field ofmicroelectronic devices, in particular, to contacts and contact holesfor microelectronic devices.

BACKGROUND

The demand for increasingly smaller devices has posed a number ofchallenges at least in terms of manufacturing, particular to the variousphotolithographic operations generally needed for patterning intricatefeatures. Forming high-density contact holes, for example, may belimited by the optical resolution capabilities of photolithographicexposure tools. Although there exist advanced photolithography toolsthat employ reduced wavelengths and have high numerical aperture values,these factors may still be insufficient to effect onto a photoresistlayer the required exposure for producing the desired contact holedensity and/or size. Accordingly, effectively patterning high-densityand high aspect ratio contact holes is of substantial importance.

SUMMARY OF THE INVENTION

In view of the problems in the state of the art, embodiments of theinvention are directed to methods for forming high-density contact holesand contacts. More specifically, with the foregoing and other items inview, there is provided, in accordance with various embodiments of theinvention, a method comprising depositing a photoresist material over adielectric layer; patterning the photoresist material to reveal firstportions of the dielectric layer at a first plurality of locations;patterning the photoresist material to reveal second portions of thedielectric layer at a second plurality of locations; and etching therevealed first and second portions of the dielectric layer to formcorresponding first and second pluralities of contact holes.

In various embodiments, patterning the photoresist material to revealthe first portions may comprise exposing the photoresist material usinga first mask configured to pattern the first plurality of locations.Patterning the photoresist material to reveal the second portions maycomprise exposing the photoresist material using a second maskconfigured to pattern the second plurality of locations. In someembodiments, patterning the photoresist material to reveal the secondportions may comprise re-positioning the first mask over the photoresistmaterial for patterning the second plurality of locations.

In some embodiments, the method may comprise depositing a photoresistmaterial into the first plurality of contact holes, wherein thephotoresist material is patterned to reveal the second portions aftersaid depositing the photoresist material into the first plurality ofcontact holes.

In various embodiments, etching the revealed first portions and saidetching the revealed second portions may be performed substantiallysimultaneously.

In various embodiments, the first plurality of contact holes may have afirst contact pitch, the second plurality of contact holes may have asecond contact pitch, and the first and second plurality of contactholes together may have a third contact pitch, the third contact pitchbeing less than the first contact pitch and the second contact pitch.

In some embodiments, the method may comprise forming the dielectriclayer over a substrate, wherein the substrate is a memory deviceincluding a plurality of memory cells. In various embodiments, the firstand second plurality of contact holes may be formed over the memorycells. In various embodiments, a metal may be deposited in the first andsecond plurality of contact holes to form corresponding first and secondpluralities of contacts.

There is also provided, in accordance with various embodiments, a methodcomprising depositing a first dummy layer over a substrate to form afirst pattern; depositing a second dummy layer over the substrate toform a second pattern, the second pattern overlapping the first patternat a plurality of locations; etching the first and second dummy layersto form a plurality of posts at the plurality of locations; forming adielectric layer over the substrate; and etching the posts to form aplurality of contact holes in the dielectric layer.

In various embodiments, the first pattern may comprise a plurality oflines of the first dummy layer, and the second pattern may comprise aplurality of lines of the second dummy layer.

In various embodiments, forming the dielectric layer may compriseforming the dielectric layer over the substrate and at least one of theposts, and the method may further comprise removing a portion of thedielectric layer to expose a top surface of the at least one post. Invarious embodiments, removing the portion of the dielectric layer maycomprise chemically and mechanically planarizing the portion of thedielectric layer.

In some embodiments, the first and the second dummy layers may comprisepolysilicon.

In various embodiments, the substrate may comprise a memory deviceincluding a plurality of memory cells, and the plurality of contactholes may be formed over the memory cells. In some embodiments, a metalmay be deposited in the first and second plurality of contact holes toform corresponding first and second pluralities of contacts.

There is also provided, in accordance with various embodiments, a methodcomprising exposing a first pattern of a photoresist material to a firstenergy, the first energy being less than an activation energy doserequired to develop the photoresist material; exposing a second patternof the photoresist material to a second energy, the second patternoverlapping the first pattern at a plurality of locations, and thesecond energy being less than the activation energy dose; removing thephotoresist material at the plurality of locations to reveal portions ofa dielectric layer; and etching the revealed portions of the dielectriclayer to form a plurality of contact holes.

In various embodiments, the first energy combined with the second energymay have a total energy equal to or greater than the activation energydose. In some embodiments, the first energy and the second energy mayeach be substantially half of the activation energy dose.

In various embodiments, exposing the first pattern may comprise exposingthe photoresist material using a first mask configured to form the firstpattern. In some embodiments, exposing the second pattern may compriseexposing the photoresist material using a second mask configured to formthe second pattern. In some embodiments, exposing the second pattern maycomprise re-positioning the first mask over the photoresist material forexposing the second pattern.

In various embodiments, the method may comprise forming the dielectriclayer over a substrate, wherein the substrate is a memory deviceincluding a plurality of memory cells. In various embodiments, theplurality of contact holes may be formed over the memory cells. In someembodiments, metal may be deposited into the plurality of contact holesto form corresponding plurality of contacts.

Other features that are considered as characteristic for embodiments ofthe invention are set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be readily understood by thefollowing detailed description in conjunction with the accompanyingdrawings. To facilitate this description, like reference numeralsdesignate like structural elements. Embodiments of the invention areillustrated by way of example and not by way of limitation in thefigures of the accompanying drawings.

FIG. 1A illustrates a top view of a microelectronic device including aplurality of contact holes, and FIG. 1B illustrates a cross-sectionalside view of the microelectronic device of FIG. 1A.

FIG. 2A illustrates a top view of a microelectronic device including aplurality of contact holes having a reduced contact pitch relative tothe microelectronic device of FIGS. 1A-1B, and FIG. 2B illustrates across-sectional side view of the microelectronic device of FIG. 2A.

FIGS. 3A-3F illustrate various stages of a method for forminghigh-density contact holes in accordance with various embodiments of thepresent invention.

FIGS. 4A-4I illustrate various stages of another method for forminghigh-density contact holes in accordance with various embodiments of thepresent invention.

FIGS. 5A-5H illustrate various stages of another method for forminghigh-density contact holes in accordance with various embodiments of thepresent invention.

FIGS. 6A and 6B illustrate various stages of a method for forminghigh-density contacts in accordance with various embodiments of thepresent invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof wherein like numeralsdesignate like parts throughout, and in which is shown by way ofillustration embodiments in which the invention may be practiced. It isto be understood that other embodiments may be utilized and structuralor logical changes may be made without departing from the scope of thepresent invention. Therefore, the following detailed description is notto be taken in a limiting sense, and the scope of embodiments inaccordance with the present invention is defined by the appended claimsand their equivalents.

The description may use the phrases “in an embodiment,” “inembodiments,” or “in various embodiments,” which may each refer to oneor more of the same or different embodiments. Furthermore, the terms“comprising,” “including,” “having,” and the like, as used with respectto embodiments of the present invention, are synonymous. The phrase“A/B” means A or B. For the purposes of the present invention, thephrase “A and/or B” means “(A), (B), or (A and B).” The phrase “at leastone of A, B, and C” means “(A), (B), (C), (A and B), (A and C), (B andC), or (A, B, and C).” The phrase “(A)B” means “(B) or (AB),” that is, Ais an optional element.

The terms chip, die, integrated circuit, monolithic device,semiconductor device, and microelectronic device are often usedinterchangeably in the microelectronics field. The present invention isapplicable to all of the above as they are generally understood in thefield.

Various embodiments of the present invention are directed to methods forpatterning high-density contact holes. Illustrated in FIG. 1A is amicroelectronic device 100 including a dielectric layer 102 formed overa substrate 104. Typically, one or more other device layers may bedisposed between dielectric layer 102 and substrate 104. For clarity,however, dielectric layer 102 is illustrated as being directly onsubstrate 104.

A number of contact holes 106 are formed in dielectric layer 102.Contact holes 106 may have a pre-determined pitch between contact holes106. As illustrated in FIG. 2A, however, microelectronic device 200includes a higher density of contact holes 206, having a reduced pitchbetween contact holes 206. Microelectronic device 200 includes, likemicroelectronic device 100, a dielectric layer 202 formed over asubstrate 204. Rather than controlling various parameters of aphotolithographic exposure tool for achieving the increased contact holedensity, an exemplary method comprising patterning first portions ofdielectric layer (e.g., contact holes 106 of FIGS. 1A-1B) and secondportions of dielectric layer (e.g., the additional contact holes 206 ofFIGS. 2A-2B) in at least two operations, wherein the contact pitchachieved may be one that a photolithographic exposure tool may beoptically incapable of resolving.

Illustrated in FIGS. 3A-3F are cross-sectional views of amicroelectronic device 300 after various operations associated withforming high-density contact holes. In various embodiments and asillustrated at FIG. 3A, a dielectric layer 302 may be formed over asubstrate 304. Substrate 304 used for various embodiments of the presentinvention may be any suitable substrate including, for example, silicon,geranium, gallium arsenide, and the like. Likewise, dielectric layer 302for various embodiments described herein may be formed with anydielectric material suitable for the purpose including, for example,oxide, polyimide, or the like. In some embodiments, dielectric layer 302may be an interlayer dielectric layer. It is noted that althoughdielectric layer 302 is illustrated being formed directly on substrate304, one or more device layers may intervene substrate 304 anddielectric layer 302, depending on the application.

As illustrated in FIG. 3B, a photoresist layer 306 may be formed overthe dielectric layer 302. A photoresist material suitable for formingphotoresist layer 306 may be any radiation-sensitive material suitablefor the purpose. Photoresist layer 306 may be formed from a positivephotoresist or a negative photoresist, depending on the application, andembodiments of the present invention are applicable to both. For thevarious embodiments described herein, positive photoresists areillustrated for simplicity.

Photoresist layer 306 may be patterned with a first pattern to revealfirst portions 308 of dielectric layer 302 at a first plurality oflocations, as illustrated at FIG. 3C. The first revealed portions 308may correspond to locations of contact holes 106 illustrated in FIGS.1A-1B, and having a first contact pitch.

According to various embodiments, patterning photoresist layer 306 toreveal first portions 308 may comprise exposing the photoresist layer306 using a first mask (not illustrated) configured to pattern the firstplurality of locations. A mask used for any one or more of variousoperations described herein may be any suitable patterning apparatussuch as, for example, a reticle. Photoresist materials used for formingphotoresist layers for any one or more of various operations describedherein may be exposed to any radiation, and for any amount of time,suitable to cause the photoresist material to be removable, at theexposed locations (or unexposed locations with negative photoresist),during a develop operation.

Patterning photoresist layer 306 may include one or more developmentoperations for removing the exposed locations of photoresist layer 306(or unexposed locations for negative photoresist).

As illustrated in FIG. 3D, photoresist layer 306 may be patterned with asecond pattern to reveal second portions 310 of dielectric layer 302 ata second plurality of locations. The second revealed portions 310 maycorrespond to locations of the additional contact holes 206 illustratedin FIGS. 2A-2B, and having a second contact pitch.

According to various embodiments, patterning photoresist layer 306 toreveal second portions 310 may comprise exposing photoresist layer 306using a second mask (not illustrated) configured to pattern the secondplurality of locations. In various other embodiments, the first maskused for forming the first pattern may be re-used for forming the secondpattern by re-positioning the first mask over the photoresist layer 306,by moving the first mask or the substrate, to a position suitable forpatterning the second pattern. One or more development operations may beperformed for removing the exposed locations of photoresist layer 306.

Although FIGS. 3C and 3D depict separate patterning operations, withfirst portions 308 of dielectric layer 302 being revealed first andsecond portions 310 of dielectric layer 302 being revealed second,various ones of the operations may be performed in another order or maybe combined into fewer operations. For example, photoresist layer 306may be exposed with the first pattern, then exposed with the secondpattern, and then may be developed by simultaneously removing theexposed locations.

As illustrated in FIG. 3E, revealed first and second portions 308, 310of dielectric layer 302 may be etched to form corresponding first andsecond pluralities of contact holes 312, 314. The revealed first andsecond portions 308, 310 may be etched in separate operations or may beperformed substantially simultaneously. For example, revealed firstportions 308 may be etched after patterning the first pattern and priorto patterning the second pattern, or alternatively, revealed first andsecond portions 308, 310 may be etched substantially simultaneouslyafter patterning both first and second patterns.

In some embodiments, revealed first portions 308 may be etched to formfirst contact holes 312, and prior to revealing second portions 310,photoresist material may be formed into at least the first contact holes312. The second portions 310 of dielectric layer 302 may then berevealed and the revealed second portions 310 etched to form secondcontact holes 314.

As noted herein, first contact holes 312 may have a first contact pitchand second contact holes 314 may have a second pitch. According tovarious embodiments, the first and second pluralities of contact holes312, 314 together may have a third contact pitch. The first pitch andthe second pitch are both greater than the third pitch, thus allowingfor a contact pitch greater that that which may be permitted withcertain photolithographic tools. Referring back to FIG. 2A, for example,contact holes are formed having a contact pitch of x, yet those contactholes were formed by twice patterning contact holes having a contactpitch of 1.4x (i.e., √{square root over (x²+x²)}). Accordingly, aphotolithographic exposure tool need only be capable of opticallyresolving a pattern for forming a contact pitch of 1.4x, yet may stillform contact holes having a reduced contact pitch of x.

In various embodiments, high-density contact holes may be formed byusing dummy layers in contrast to the multi-step exposure approachdiscussed above. In contrast to depending on the optical resolutioncapabilities of photolithographic exposure tools, this embodiment allowsfor forming contact holes having a contact pitch limited only by thesize and/or spacing of dummy layer patterns. In various ones of theseembodiments, intersecting locations of the dummy layers are thelocations of later-formed contact holes. Accordingly, high-densitycontact holes may be possible regardless of the photolithographicexposure capabilities.

FIGS. 4A-4I illustrate various views of a microelectronic device 400after various operations associated with forming high-density contactholes using dummy layers. As illustrated in FIG. 4A (top view) and FIG.4B (cross-sectional side view), a first dummy layer 402 is depositedover a substrate 404 in a first pattern. In this embodiment, the firstpattern includes a number of lines, but other embodiments of the firstpattern may comprise any other suitable pattern and may depend on theparticular application. It should be noted that although the illustratedembodiment depicts first dummy layer 402 being formed directly onsubstrate 404, a microelectronic device may typically include one ormore device layers disposed therebetween. The condensed illustrationsimplifies the structure for the sake of clarity.

A second dummy layer 406 is formed over the substrate 404 and over someportions of first dummy layer 402, as illustrated in FIG. 4C (top view)and 4D (cross-sectional side view). In the illustrated embodiment, firstdummy layer 402 is formed as a number of lines in the y-direction andthe second dummy layer 406 is formed as a number of lines in thex-direction, forming a plurality of intersecting locations 408. Asdepicted in FIG. 4D, the intersecting locations 408 effectively includesubstantially a double layer of material while the non-intersectinglocations include substantially a single layer of material.

The first and second dummy layers 402, 406 may be formed from anysuitable material. In various embodiments, one or both of the dummylayers 402, 406 may be formed using polysilicon. Other materials may besimilarly suitable. For example, silicon nitride may be used for formingdummy layers 402, 406.

The first and second dummy layers 402, 406 may be etched to form aplurality of posts 410 at the plurality of intersecting locations 408 asillustrated in FIG. 4E (top view) and FIG. 4F (cross-sectional sideview). The plurality of posts 410 should generally be disposed atlocations at which a corresponding plurality of contact holes aredesired because the posts will be etched, as discussed more fully below,for forming the contact holes. Accordingly, the first and second dummylayers 402, 406 may be configured to intersect at locations wherecontact holes are desired.

For forming the posts 410, the etch operation may be adapted to etchaway a thickness of polysilicon, or whichever material is used forforming dummy layers 402, 406, equal to the thickness of either thefirst dummy layer 402 or the second dummy layer 406, whichever isgreater. The etch operation, however, should not etch away so muchpolysilicon as to leave posts 410 of an insufficient height. In otherwords, the etch operation should be adapted to etch a thickness ofpolysilicon at least equal to the thicker of the dummy layers 402, 406,but no more than an amount necessary to leave posts 410 at least as tallas the desired contact holes to be later formed.

A dielectric layer 412 may be formed over the substrate 404 and posts410 as illustrated at FIG. 4G, and at FIG. 4H, a portion of dielectriclayer 412 is removed to expose a top surface of posts 410. For removingthe portion of dielectric layer 412 any suitable method may be usedincluding, for example, a chemical-mechanical planarization (CMP)operation (sometimes alternatively referred to in the art as“chemical-mechanical polish”). While removing the portion of dielectriclayer 412 it may also be desirable to remove some amount of the topsurface of posts 410. Doing so may ensure full removal of dielectriclayer 412 and/or may produce a desired degree of levelness.

Posts 410 may be etched to form a plurality of contact holes 414 indielectric layer 412, the plurality of contact holes 414 correspondingto the locations of posts 410 prior to their removal, as illustrated inFIG. 4I. It should be evident that using dummy layers 402, 406 forforming posts 410, and ultimately, contact holes 414 at the locations ofposts 410, allows for forming contact holes 414 having a contact pitchlimited only by the size and/or spacing of dummy layer patterns.Accordingly, high-density contact holes 414 may be possible regardlessof photolithographic exposure capabilities.

In still further embodiments, high-density contact holes may be formedusing a multi-step exposure approach, wherein a first pattern is exposedto a first energy and a second pattern is exposed to a second energy,the first and the second energy each being less than a removal energydose required to develop the photoresist material but combined may beequal to or greater than the required removal energy dose. Similarly tothe multi-step exposure approach described with reference to FIGS.3A-3F, this exemplary method may achieve a tighter contact hole pitchthan that which may be permitted by a particular photolithographicexposure tool due at least in part to the contact hole pattern beingbroken down into at least two separate exposures, each exposure having acontact hole pattern having an increased contact hole pitch.

Illustrated in FIG. 5A is a cross-sectional side view of amicroelectronic device 500 including a substrate 502, a dielectric layer504 formed over substrate 502, and a photoresist material 506 formedover dielectric layer 504. As noted previously, any number of devicelayers may intervene substrate 502 and dielectric layer 504, and/ordielectric layer 504 and photoresist material 506, depending on theapplication.

A first pattern may be exposed on photoresist material 506 using a firstenergy 508. The first pattern may be effected by way of a mask 510 orthe like. FIG. 5B illustrates a top view of microelectronic device 500depicting for illustrative purposes the exposed first pattern 512 onphotoresist material 506. Although the illustrated first pattern 512generally comprises a number of lines in the y-direction, any suitablepattern may be employed, depending on the application.

First energy 508 may be an energy less than that required to developphotoresist material (hereinafter “activation energy dose”). Theactivation energy dose may be the amount of energy that must be providedto photoresist material 506 to invoke a chemical change sufficient toallow photoresist material 506 to either be removed (positivephotoresist) or to become resistant to removal (negative photoresist)during development.

Turning now to FIG. 5C, illustrated is a cross-sectional side view ofmicroelectronic device 500, wherein a second pattern is exposed onphotoresist material 506 using a second energy 514. The second patternmay be effected by way of a mask 516 (illustrated by hatched lines) orthe like. FIG. 5D illustrates a top view of microelectronic device 500depicting for illustrative purposes the exposed second pattern 518 onphotoresist material 506. Although the illustrated second pattern 518generally comprises a number of lines in the x-direction, any suitablepattern may be employed, depending on the application, so long as firstpattern 512 and second pattern 518 intersect at one or more locations520, as explained more fully below.

In various embodiments, mask 510 used for forming first pattern 512 maybe re-used for forming second pattern 518 by re-positioning mask 510over photoresist layer 506, by moving mask 510 or the substrate 502, toa position suitable for patterning second pattern 518.

Like first energy 508, second energy 514 may be an energy value lessthan the activation energy dose. Accordingly, those areas of photoresistmaterial 506 receiving less than the activation energy dose may not beexpected to be removed during a development operation, wherein adeveloper solution is usually applied to photoresist material 506resulting in a pattern.

At intersecting locations 520 (see FIG. 5D), however, energy has beenapplied thereto, that is substantially equal to first energy 508 plussecond energy 514. If the energy value of first energy 508 combined withsecond energy 514 is at least equal to the activation energy dose, itwould be expected, then, that those intersecting locations 520 ofphotoresist material 506 would be removed during a developmentoperation. For example, if first energy 508 and second energy 514 aresubstantially half the value of the activation energy dose, or someother combination of values equal to or exceeding the activation energydose, then combined they would be sufficient to achieve the activationenergy dose. FIG. 5E (top view) and FIG. 5F (cross-sectional side view)illustrate photoresist material 506 having been removed for theintersecting locations 520, yet remaining in non-intersecting locations522. As illustrated, portions 524 of dielectric layer 504 are revealedafter removal of photoresist material 506

In various embodiments, photoresist material 506 may be exposed to morethan first pattern of first energy and second pattern of second energy.For example, a third pattern may be exposed on photoresist material 506using a third energy, and so on. In these embodiments, the energy valuesof first energy 508, second energy 514, third energy, and so on, wouldneed to be adjusted to provide the desired level of energy atintersecting locations 520 in order to achieve the activation energydose thereat.

As illustrated at FIG. 5G, revealed portions 524 of dielectric layer 504may be etched to form corresponding contact holes 526. Using themulti-step exposure approach may allow for formation of high-densitycontact holes having a contact hole pitch limited only by the design ofthe exposed patterns and perhaps the number of exposures. Accordingly,high-density contact holes may be possible regardless ofphotolithographic exposure capabilities.

In various embodiments, the formed contact holes may be used for formingmetal contacts for electrically interconnecting various device layers ofa microelectronic device. Accordingly, high-density contacts may beformed.

High-density contacts may be particularly useful for memoryapplications. Memory cells are generally formed in dense arrays and thusmay also require contacts formed with a density difficult to achievewith various other methods.

An exemplary microelectronic device 600 is illustrated in FIG. 6A.Microelectronic device 600 includes a substrate 602 having a number ofmemory cells 604. As illustrated, a dielectric layer 606 has been formedover substrate 602, and high-density contact holes 608 have been formedin dielectric layer 606 over memory cells 604. One or more device layersmay be included between substrate 602 and dielectric layer 606,depending on the application. Any one or more various methods asdescribed herein may be used for forming contact holes 608.

According to various embodiments, metal may be deposited into contactholes 608 for forming contacts 610, as illustrated in FIG. 6B. Metalcontacts 610 may be formed using any material suitable for the purpose.For example, the metal may be a selected one or more of copper,platinum, aluminum, and the like. Other materials may be similarlysuitable.

Although certain embodiments have been illustrated and described hereinfor purposes of description of a preferred embodiment, it will beappreciated by those of ordinary skill in the art that a wide variety ofalternate and/or equivalent embodiments or implementations calculated toachieve the same purposes may be substituted for the embodiments shownand described without departing from the scope of the present invention.Those with skill in the art will readily appreciate that embodiments inaccordance with the present invention may be implemented in a very widevariety of ways. This application is intended to cover any adaptationsor variations of the embodiments discussed herein. Therefore, it ismanifestly intended that embodiments in accordance with the presentinvention be limited only by the claims and the equivalents thereof.

1. A method comprising: depositing a photoresist material over adielectric layer; patterning the photoresist material to reveal firstportions of the dielectric layer at a first plurality of locations;patterning the photoresist material to reveal second portions of thedielectric layer at a second plurality of locations; etching therevealed first and second portions of the dielectric layer to formcorresponding first and second pluralities of contact holes; anddepositing another photoresist material into the first plurality ofcontact holes, wherein the photoresist material is patterned to revealthe second portions after said depositing the another photoresistmaterial into the first plurality of contact holes.
 2. The method ofclaim 1, wherein said patterning the photoresist material to reveal thefirst portions comprises exposing the photoresist material using a firstmask configured to pattern the first plurality of locations.
 3. Themethod of claim 2, wherein said patterning the photoresist material toreveal the second portions comprises exposing the photoresist materialusing a second mask configured to pattern the second plurality oflocations.
 4. The method of claim 2, wherein said patterning thephotoresist material to reveal the second portions comprisesre-positioning the first mask over the photoresist material forpatterning the second plurality of locations.
 5. The method of claim 1,wherein the first plurality of contact holes has a first contact pitch,the second plurality of contact holes has a second contact pitch, andthe first and second plurality of contact holes together have a thirdcontact pitch, the third contact pitch being less than the lower of thefirst contact pitch and the second contact pitch.
 6. The method of claim1, further comprising forming the dielectric layer over a substrate,wherein the substrate forms a memory device including a plurality ofmemory cells, and wherein the first and second pluralities of contactholes are formed over the memory cells.
 7. The method of claim 6,further comprising depositing a metal in the first and secondpluralities of contact holes to form corresponding first and secondpluralities of contacts.
 8. A method comprising: depositing a firstdummy layer over a substrate to form a first pattern; depositing asecond dummy layer over the substrate to form a second pattern, thesecond pattern overlapping the first pattern at a plurality oflocations; etching the first and second dummy layers to form a pluralityof posts at the plurality of locations; forming a dielectric layer overthe substrate; and etching the posts to form a plurality of contactholes in the dielectric layer.
 9. The method of claim 8, wherein thefirst pattern comprises a plurality of lines of the first dummy layer,and wherein the second pattern comprises a plurality of lines of thesecond dummy layer.
 10. The method of claim 8, wherein said forming thedielectric layer comprises forming the dielectric layer over thesubstrate and at least one of the posts, and wherein the method furthercomprises removing a portion of the dielectric layer to expose a topsurface of the at least one post.
 11. The method of claim 10, whereinremoving the portion of the dielectric layer comprises chemically andmechanically planarizing the portion of the dielectric layer.
 12. Themethod of claim 8, wherein the first and the second dummy layerscomprise polysilicon.
 13. The method of claim 8, wherein the substrateforms a memory device including a plurality of memory cells, and whereinthe plurality of contact holes are formed over the memory cells.
 14. Themethod of claim 13, further comprising depositing a metal in theplurality of contact holes to form corresponding plurality of contacts.15. A method comprising: exposing a first pattern of a photoresistmaterial to a first energy, the first energy being less than anactivation energy dose required to develop the photoresist material;exposing a second pattern of the photoresist material to a secondenergy, the second pattern overlapping the first pattern at a pluralityof locations, and the second energy being less than the activationenergy dose required to develop the photoresist material; removing thephotoresist material at the plurality of locations to reveal portions ofa dielectric layer; and etching the revealed portions of the dielectriclayer to form a plurality of contact holes.
 16. The method of claim 15,wherein the first energy combined with the second energy have a totalenergy equal to or greater than the activation energy dose required todevelop the photoresist material.
 17. The method of claim 16, whereinthe first energy and the second energy are each substantially half ofthe activation energy dose required to develop the photoresist material.18. The method of claim 15, wherein said exposing the first patterncomprises exposing the photoresist material using a first maskconfigured to form the first pattern.
 19. The method of claim 18,wherein said exposing the second pattern comprises exposing thephotoresist material using a second mask configured to form the secondpattern.
 20. The method of claim 18, wherein said exposing the secondpattern comprises re-positioning the first mask over the photoresistmaterial for exposing the second pattern.
 21. The method of claim 15,further comprising forming the dielectric layer over a substrate,wherein the substrate forms a memory device including a plurality ofmemory cells, and wherein the plurality of contact holes are formed overthe memory cells.
 22. The method of claim 21, further comprisingdepositing a metal in the plurality of contact holes to formcorresponding plurality of contacts.